1. Field of the Invention
The present invention disclosed in the specification relates to a method of fabricating a semiconductor device by using a silicon film formed on a substrate of glass or the like. For example, the present invention relates to a method of fabricating a thin film transistor on a glass substrate.
2. Description of the Related Art
A technology of fabricating a thin film transistor on a glass substrate or a quartz substrate is known.
Although the mainstream technology is a thin film transistor using an amorphous silicon film, recently, a silicon film having crystalline performance has also been fabricated.
A thin film transistor using a silicon film having crystalline performance has shown good results.
However, it is difficult to form a silicon film having high crystalline performance uniformly in a large area.
Further, it is desirable to use an inexpensive glass substrate as a substrate. However, a technology of providing a crystalline silicon film at a processing temperature that the glass substrate can withstand is needed. This is an important technological problem.
A laser annealing process can be used as a process having a process temperature that the glass substrate can withstand. The laser annealing process is superior in that almost no thermal impact is caused in the substrate.
However, the following problems exist.
(1) It is difficult to carry out laser annealing uniformly over a large area.
(2) Oscillation intensity of the laser beam used in the process is unstable.
One known technology is disclosed in Unexamined Published Japanese Patent Application No. 7-321339 as a means for resolving these problems.
In this technology, a crystalline silicon film is provided by performing a heating treatment at a temperature that a glass substrate can withstand and by introducing a metal element for promoting the crystallization of silicon, such as nickel or the like, into an amorphous silicon film.
When the technology disclosed in Unexamined Published Japanese Patent Application No. 7-321339 is used, the resulting crystalline silicon film has excellent quality not previously obtained (meaning that not only is crystalline performance excellent, but a TFT (Thin Film Transistor) having excellent properties results) over a large area.
However, a problem of dispersion or unstableness still exists, which seems to be caused by the metal element remaining in the silicon.
The present invention disclosed in the specification provides the means for resolving the problem.
In one aspect, the present invention provides a method of fabricating a semiconductor device comprising:
a step of introducing a metal element for promoting the crystallization of silicon into an amorphous silicon film;
a step of providing a crystalline silicon film by crystallizing the amorphous silicon film by performing a heating treatment;
a step of masking a portion of the crystalline silicon film and accelerating and implanting ions of an impurity element to another portion;
a step of moving the metal element for promoting the crystallization of silicon present in the crystalline silicon film by performing a heating treatment; and
a step of forming an activation layer of a semiconductor device by utilizing the masked region.
In another aspect, the present invention provides a method of fabricating a semiconductor device comprising:
a step of introducing a metal element for promoting the crystallization of silicon into an amorphous silicon film;
a step of providing a crystalline silicon film by crystallizing the amorphous silicon film by performing a heating treatment;
a step of irradiating a laser beam on the crystalline silicon film;
a step of masking a portion of the crystalline silicon film and accelerating and implanting ions of an impurity element to another portion;
a step of moving the metal element for promoting the crystallization of silicon present in the crystalline silicon film by performing a heating treatment; and
a step of forming an activation layer of a semiconductor device by utilizing the masked region.
In another aspect, the present invention provides a method of fabricating a semiconductor device comprising:
a step of introducing a metal element for promoting the crystallization of silicon into an amorphous silicon film;
a step of providing a crystalline silicon film by crystallizing the amorphous silicon film by performing a heating treatment;
a step of masking a portion of the crystalline silicon film and accelerating and implanting ions of an impurity element to another portion;
a step of moving the metal element from the masked region to the region where the impurity element has been doped by performing a heating treatment; and
a step of forming an activation layer of a semiconductor device by utilizing the masked region.
In another aspect, the present invention provides a method of fabricating a semiconductor device comprising:
a step of selectively introducing a metal element for promoting the crystallization of silicon into an amorphous silicon film formed on a substrate having an insulating surface;
a step of providing a crystalline silicon film by making crystals grow from a region where the metal element has been selectively introduced in a direction in parallel with the substrate by performing a heating treatment;
a step of masking a portion of the crystalline silicon film and accelerating and implanting ions of an impurity element to another portion;
a step of moving the metal element for promoting the crystallization of silicon present in the masked crystalline silicon film to the other portion by performing a heating treatment; and
a step of forming an activation layer of a semiconductor device by utilizing the masked region.
In another aspect, the present invention provides a method of fabricating a semiconductor device comprising:
a step of selectively introducing a metal element for promoting the crystallization of silicon into an amorphous silicon film formed on a substrate having an insulating surface;
a step of providing a crystalline silicon film by making crystals grow from a region where the metal element has been selectively introduced in a direction in parallel with the substrate by performing a heating treatment;
a step of irradiating a laser beam on the crystalline silicon film;
a step of masking a portion of the crystalline silicon film and accelerating and implanting ions of an impurity element to another portion;
a step of moving the metal element for promoting the crystallization of silicon present in the crystalline silicon film to the region where the impurity element has been accelerated and implanted by performing a heating treatment; and
a step of forming an activation layer of a semiconductor device by utilizing the masked region.
In another aspect, the present invention provides a method of fabricating a semiconductor device comprising:
a step of selectively introducing a metal element for promoting the crystallization of silicon into an amorphous silicon film formed on a substrate having an insulating surface;
a step of providing a crystalline silicon film by making crystals grow from a region where the metal element has been selectively introduced in a direction in parallel with the substrate by performing a heating treatment;
a step of masking a portion of the crystalline silicon film and accelerating and implanting ions of an impurity element to another portion;
a step of moving the metal element from the masked region to a region where the impurity element has been doped by performing a heating treatment; and
a step of forming an activation layer of a semiconductor device by utilizing the masked region.
During the step of moving the metal element, it is preferable to perform the heating treatment in an atmosphere including oxygen.
Further, it is preferable to utilize Ni (nickel) as the metal element for promoting the crystallization of silicon.
Further, as a metal element for promoting the crystallization of silicon, one or more elements selected from the group consisting of Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt, Cu and Au can be utilized.
Furthermore, it is preferable to utilize P (phosphor) as the impurity element that is accelerated and implanted into the crystalline silicon film. Other than P, a material selected from a group consisting of N, As, Sb and Bi, which belong to the same periodic group as P, can be used.
Further, it is important to select the masked region to avoid the region where the metal element has selectively been introduced.